In 1842, finding that his name was being used again in connection with the office of Lieut. Governor, he declined the nomination in advance of the meeting of the convention, but was nevertheless nominated unanimously and by acclamation, and compelled by circumstances to accept, and was elected by 25,000 majority. The office of Lieut. Governor made him President of the Senate, Presiding Judge of the Court for the Correction of Errors, member of the Canal Board, Regent of the University, etc., etc. His term of office expired Dec. 31, 1844, and he declined a reëlection. It was held during a somewhat stormy period in the history of the State, but was so discharged as to add to his reputation with the people and his standing with the Democratic party. As the presiding officer of the Senate, in particular, he showed a decision, firmness and dignity of character which elicited the admiration and approval of opponents as well as friends. At the election in 1844, he opened the Presidential campaign in New York on the annexation of Texas, which he warmly advocated against the opinion of many leading Democrats. He spent the whole campaign upon the stump; was one of the Democratic _State_ electors, and united in casting the vote of the State for Polk and Dallas. About the 1st of December, 1844, he was appointed by Governor Bouck United State senator in place of N. P. Tallmadge, resigned, and immediately proceeded to Washington and took his seat as such. Governor Tallmadge's term expired on the 4th of March, 1845. On the meeting of the Legislature in January, 1845, he was elected for the unexpired term of Governor Tallmadge, and subsequently for the regular term of six years, from 4th March, 1845; during which term he remained in the Senate, closing his public service 4th March, 1851. For a number of years he was Chairman of the Committee of Finance in the Senate, but declined it, and all committee service, the last short session of the term. He was a member of the committee to bear the remains of Mr. Calhoun to his native State, and discharged the duty with the almost filial regard he felt for the great man who had been called away from the field of his public labors. This is the only time he ever visited the South; but, though necessarily a hasty trip, he received many tokens of public and private appreciation. In 1847, he introduced into the Senate, and advocated in an able speech, his celebrated resolution on the acquisition and annexation of territory, and asserting, in opposition to the doctrines of the Wilmot Proviso, the principles of "popular sovereignty," which formed the basis of the adjustment of 1850, and has since been so fully approved by the people. He opposed the Oregon Treaty, which surrendered several degrees of American territory to Great Britain. He opposed the Clayton-Bulwer Treaty, which he conceived to be a cheat, and has been a constant source of embarrassment and misunderstanding between the two governments.